Bit the bullet and emailed SOA...interesting!
I have a MY09 WRX. I am hearing that you are not supposed to use full synthetic oil for the first few changes. Please confirm whether or not this is true. Thank you.
“Thank you for visiting the Subaru Web site and congratulations on the purchase of your 2009 WRX. We wish you the best with it!!
As for synthetic oil, this is your decision. Our Technical Services Department advised that if you do decide to use synthetic oil, that you always use it because your engine will become accustomed to it. The same goes if you decide to use 'regular' oil.
We recommend that you first change the oil in your 2009 WRX at 3,750 miles or 3.75 months, whichever comes first. We STRONGLY recommend that you at least wait until the break-in period of 1,000 miles is surpassed.
The break-in period of the engine requires that a given amount of friction exists between components. The piston rings need to rub against the cylinder wall to break-in or finely tune the machine mating between the two metal parts. To properly seat all mechanical components, a certain amount of friction is required between the metal parts. Since synthetic oil has a lower friction rating than regular oil, we recommend that Subaru owners wait until after the 1,000 mile break-in period to switch to synthetic engine oil.
Synthetic engine oils can be used in our engines if the user follows the engine oil recommendations prescribed in the Owner's Manual. Subaru has not tested the compatibility of all synthetic oils with engine seals, but the petroleum industry does adhere to standards for the refining process which meet Subaru requirements. Subaru does not guarantee the performance of any brand of any engine oil.
Engine Oil Guidelines: - only use engine oil that meets or exceeds the API classification designated in the Owner's Manual for the vehicle - only use engine oil that meets the VISCOSITY requirements for the ambient temperatures under which the vehicle will be operated as outlined in the Owner's Manual - THE ENGINE OIL MUST BE CHANGED AT THE INTERVALS SPECIFIED IN THE WARRANTY AND MAINTENANCE BOOKLET FOR THE VEHICLE. SOME SYNTHETIC OIL REFINERS RECOMMEND EXTENDED OIL CHANGE INTERVALS. SUBARU DOES NOT RECOMMEND ANY DEVIATION FROM THE SPECIFIED INTERVALS IN THE OWNER'S MANUAL.
Thank you for the opportunity to be of assistance. If you need any future assistance, please let us know.”
So my take:
Sounds like the thin break-in oil is purposeful to mate the metal parts. The friction is NECESSARY! Crazy.
Also, it sounds like they are protecting themselves in case something goes wrong with using synthetic afterwards, the lawyers probably wrote that response. I guess I won't change my oil 'till 2K-ish now. Still dont' know whether to use synthetic or not. Sheesh!!!